The transit agency says the enforcement is intended to keep buses moving through lanes that are often blocked by cars stopping to pick up passengers, make deliveries or retrieve food. Those obstructions can force buses back into traffic and leave passengers getting off in the roadway, said Ryan Coholan, the MBTA’s chief operating officer.

The MBTA has about 40 miles of bus lanes and 7,000 bus stops across Greater Boston. About one-third of its buses will carry cameras for the program. The cameras are designed to record only near bus stops, using GPS-defined zones to activate recording as a bus approaches.

Footage flagged as a possible violation will be reviewed by an MBTA staff member before the agency decides whether to issue a ticket. Reviewers can reject cases involving circumstances such as a police officer responding to an emergency, said Alex Hallowell, an MBTA official. Drivers who receive a fine can appeal it.

The MBTA says license-plate information and video remain in its database and are not shared or sold. The agency says recordings and related personal information are deleted after 120 days.

Drivers may not travel along a bus lane unless they are in an emergency vehicle or moving out of the way of one. They may cross a lane to parallel park, but cannot stop in it. Drivers may also enter a bus lane to turn, but must wait until the road markings or signs permit the move.

Some drivers oppose dedicating road space to buses. A Brighton motorist interviewed about the change called the lanes a nuisance and said he wanted them removed. MBTA officials say they expect enforcement to encourage drivers to respect the lanes.